1. Field of the Invention
The present invention relates to a roller chain with low wear pivot connections.
2. Description of the Prior Art
Two types of chain in current use are the silent chain and the roller chain. A silent chain (as shown, for example, in U.S. Pat. No. 3,742,776) consists of links having teeth which engage with the teeth of a sprocket on which the chain is received. The links of a silent chain consist of a first group of links mounted on two pins, one at each end of the first group, and a second group of links mounted on two pins, one at each end of the second group. A first and second pin are received in rocking engagement at a pivot joint between the groups in aligned openings in both groups of links to pivotally connect the first group of links to the second group of links. The two groups of links are intermeshed at the pivot joint with the first group of links extending from the pivot joint in one direction and the second group of links extending from the pivot joint in the opposite direction. The rocking engagement between the two groups of links produces a low incidence of wear at the pivot joint between the two groups of links. The chain is made up of alternate first and second groups of links with a pivot joint between adjacent groups of links.
A typical roller chain (as shown, for example, in the U.S. Pat. No. 3,895,137) consists of alternate bushing links and pin links. The bushing links (which define inner links) consist of spaced sidebars with bushings tightly received in openings at each end of sidebars. The pin links (which define outer links) consist of spaced sidebars with pins tightly received in openings at each end of the sidebars. The pins are rotatably received in the bushings to connect the pin links pivotally to the bushing links in alternate arrangement. Rollers are provided on the bushings, and when the roller chain is received on a sprocket, the teeth of the sprocket are received between the laterally spaced sidebars and the longitudinally spaced rollers.
Efforts have heretofore been made to provide in a roller chain, the smooth, low wear connecting joint of the silent chain. These efforts have produced hybrid chains, which can be referred to as dual pin roller chains, such as those shown in U.S. Pat. Nos. 663,352; 663,353; 866,980; 3,540,302; and 3,595,099. By way of example, the dual pin roller chain of U.S. Pat. No. 3,595,099 has, at each pivot joint, a pair of complementary pins, one of which has a concave contact surface and the other of which has a convex contact surface. As the adjacent links pivot with respect to each other, one of said contact surfaces slides on the other of said contact surfaces to provide the required articulation of the chain.
In the U.S. Pat. No. 3,540,302, there is shown a dual pin roller chain in which sliding friction at the pin contact faces has been avoided. However, since the pins of this patent are mounted loosely in the side bars, rubbing friction is inevitable during articulation of the chain.